ABSTRACT CAREER GOALS: Dr. Sharir is determined to become an independent researcher, to investigate the molecular and biomechanical bases of mouse tooth regeneration and to apply this knowledge for translational purposes. CANDIDATE BACKGROUND: Dr. Sharir graduated from the Koret School of Veterinary Medicine in Israel and worked in a private animal hospital, where he gained clinical experience. He did his graduate research in the laboratories of Dr. Ron Shahar at The Hebrew University of Jerusalem and Dr. Elazar Zelzer at The Weizmann Institute of Science. He studied the role of muscle force in skeletogenesis and gained experience in developmental biology, genetics and bone mechanobiology. Dr. Sharir then joined Dr. Ophir Klein's laboratory at UCSF to study the mechanisms underlying the ability of stem cells (SC) to regenerate dental tissues, which is an excellent model system for in vivo exploration of SC behavior. In particular, Dr. Sharir studies the mechanisms that control the balance between self-renewal and differentiation of dental epithelium stem cells (DESCs). His preliminary findings question the common view of DESCs as slow-cycling, asymmetrically dividing cells, inspiring new directions to be explored in this proposal. RESEARCH PLAN: Dr. Sharir hypothesizes that the mouse incisor epithelium is maintained by a pool of actively cycling, equipotent SCs that are regulated by external mechanical forces. Aim 1 addresses the dynamics of clones derived from genetically labeled DESCs, and how these dynamics change following: 1) cytotoxic ablation of proliferating cells, or 2) pharmacologic disruption of Notch signaling. These experiments DESCs and will determine whether they are slow cycling and asymmetrically dividing, or actively-cycling and equipotent. In Aim 2, the role of mechanical forces in regulating DESC dynamics will be studied. First, the experienced by the mouse incisor will be modified by a device previously used in orthodontic tooth movement and the relationship between the applied load and DESC cycling dynamics will be examined. An RNA-seq analysis will be then performed to identify differentially regulated genes in the incisor epithelium under these load conditions. Finally, the functional role of these genes in incisor regeneration will be tested by genetic or pharmacologic approaches. This research will form the basis for further investigating the molecular and biomechanical bases of tooth regeneration, to be proposed in an R01 grant application during the fourth year of this award. will expose the location of mechanical loads TRAINING: Dr. Sharir is well-prepared to undertake this research. Nevertheless, to complete the project and achieve his long-term career goals, he will require further training in the application of quantitative tools for analyzing adult SC behavior and dental mechanobiology. To this end, Dr. Sharir has assembled a team of mentors and collaborators comprising of experts in these areas with the ability to help him obtain these critical skills, complete the project and evaluate progress. He will also attend courses relevant to these topics. In addition, through courses at UCSF and further hands-on experience, this award will help Dr. Sharir to develop his communication, writing and mentoring skills to eventually launch a fruitful independent research career. ENVIROMENT: Dr. Klein's lab and UCSF provide an intellectually stimulating, collaborative and resource-rich enviroment that is ideal for executing the proposed research and for promoting Dr. Sharir's career. The host lab is a world leader in the study of tooth SCs and is well-equipped for the proposed study. The Department of Orofacial Sciences and Program in Craniofacial Biology will provide additional resources for collaborations and learning opportunities.